A Brazilian protester holding up a photo of former President Luiz Inácio Lula da Silva in Rio de Janeiro on Friday.CreditSilvia Izquierdo/Associated Press

By Vinod Sreeharsha

March 18, 2016

RIO DE JANEIRO — A justice on Brazil’s highest court on Friday night suspended the nomination of the country’s former president to a cabinet post in President Dilma Rousseff’s government, the latest twist in a political crisis that has Latin America’s largest country on edge.

Justice Gilmar Mendes of the Supreme Federal Tribunal said he based his ruling on intercepts of telephone calls of the former president, Luiz Inácio Lula da Silva, who is the focus of corruption inquiries. Justice Mendes said the calls, including one with Ms. Rousseff, suggested an effort to obstruct an investigation into Mr. da Silva by a federal judge, Sergio Moro.

The move by the justice throws Mr. da Silva’s return to government into limbo, amid concerns that the former president might avoid efforts to arrest him by enjoying the privileged legal status of senior officials. They may only be tried by the Supreme Federal Tribunal.

Justice Mendes’s ruling needs to be reviewed and voted on by the entire nine-member court, which is on recess next week and is expected to have a regular session again on March 30. The justice had already signaled displeasure with Mr. da Silva earlier in the week because the intercepts revealed the former president, still one of Brazil’s most influential political figures, deriding the court.

The latest twist in the crisis underscores the tumult in Brazil over Mr. da Silva’s nomination. Thousands of the government’s backers had taken to the streets earlier on Friday to support Ms. Rousseff’s government as it faces a number of crises, including an impeachment effort and corruption investigations.

“This was expected,” said José Eduardo Cardozo, the solicitor general in Ms. Rousseff’s government, arguing that Justice Mendes was going against judicial precedents laid out by the high court. “We’re analyzing the best way to appeal the decision.”

The pro-government demonstrations, which followed larger antigovernment protests on Sunday, were part of another dramatic day in a week of rising political tensions.

Many of Ms. Rousseff’s supporters said they were trying to fend off an effort to oust a democratically elected leader. At a march that drew tens of thousands in São Paulo, the country’s financial capital, Raimundo Carlos, a 47-year-old supermarket owner, lashed out at Ms. Rousseff’s critics. “They’re trying to overthrow the government,” Mr. Carlos said. “I won’t accept that.”

Nearby, a message blared from a passing truck: “It’s the working class fighting for democracy.”

That sentiment, always an important part of Brazilian politics, appears to have grown stronger among some segments of the population after Ms. Rousseff named Mr. da Silva as her chief of staff, not long after the police raided his home and prosecutors announced that they were seeking to arrest him.

Mr. da Silva, the founder and face of the governing Workers’ Party, attended the march in São Paulo and spoke there. He has become embroiled in a widening investigation in the corruption and money-laundering scandal involving the state-owned oil company, Petrobras.

The president’s move to add Mr. da Silva to her cabinet granted him broad legal protections but intensified the nation’s political upheaval.

Opponents of the president have filed a number of legal challenges, one leading to a temporary injunction preventing Mr. da Silva from taking his new post.

On Wednesday, the federal judge overseeing the corruption investigation, Sergio Moro, released tapes of recorded conversations in which Mr. da Silva discussed ways to attack the officials investigating him.

But on Friday, Ms. Rousseff seemed to receive a brief respite. A higher court judge overturned a lower court’s injunction seeking to bar Mr. da Silva from taking office. That was the second time in 24 hours that lower court injunctions had been overturned on appeal, suggesting that Mr. da Silva would be likely to prevail in the courts and be able to assume his position in the cabinet.

Criticism of Judge Moro also mounted on Friday. Until recently he seemed untouchable, and he is considered a folk hero to many of Ms. Rousseff’s critics. But the judge’s critics are now contending that he may have exceeded his powers by releasing the contents of conversations between Ms. Rousseff and Mr. da Silva.

Ms. Rousseff on Friday criticized the state prosecutors and Judge Moro, saying that their actions constituted a “setback” in the country’s efforts to keep its judiciary apolitical.

The Brazilian newspaper Folha de S. Paulo, which has been highly critical of Ms. Rousseff, on Friday published a lead editorial that was unusually critical of Judge Moro.

Jill Langlois contributed reporting from São Paulo, Brazil.

A version of this article appears in print on , on Page A6 of the New York edition with the headline: Amid Scandals, Senior Judge in Brazil Suspends Ex-President’s Cabinet Nomination . Order Reprints | Today’s Paper | Subscribe